1. Field of the Invention
The present invention relates to audio signal processing, and more particularly, to an apparatus and method that amplifies the power of an audio signal.
2. Description of the Related Art
An example of many conventional audio power amplifiers that amplify the power of an audio input signal is an AF Power Amplifier (Split Power Supply) such as the STK4112II (hereinafter called a “conventional audio power amplifier”), which is a thick film hybrid integrated circuit (IC) amplifier manufactured by Sanyo Electric Co. Ltd.
The conventional audio power amplifier uses a high supply voltage when the level of an input audio signal is high, and a low supply voltage when the level of the audio signal is low so as to reduce power consumption required to amplify the power of the audio signal. For this purpose, a separate comparator is needed. The comparator determines the level of an input audio signal. Due to the comparator, the conventional audio power amplifier is expensive to manufacture, severely distorts the amplified audio signal, and causes high frequency noise to be produced due to the switching noise of the comparator, which may occur in switching and outputting different comparison results for each input audio signal.
Although the conventional audio power amplifier described above switches the supply voltage to only two levels according to the level of the audio signal, the amplifier may switch the supply voltage to more than two levels. In this case, additional comparators are needed, which aggravates the above problems due to the presence of the multiple comparators.